Search

This work demonstrates an enhancement mode heterojunction bipolar p-FET (HEB-PFET) structure with a AlGaN/GaN heterojunction bipolar transistor (HBT) integrated on the drain side. Such device design notably contributes to the ultra-high output current density, which is conventionally limited by the low hole mobility and concentration in the p-FETs. The HEB-PFET exhibits an output current density of 241 mA/mm, which is 134 times larger compared to the conventional p-FET (C-PFET) and 2.4 times of the homojunction bipolar p-FET (HOB-PFET). This can be attributed to a better current gain of HBT than homojunction bipolar transistor (BJT). An optimized HEB-PFET of 6 nm p-GaN layer beneath the gate is proposed, where ION/IOFF is >1011, and Vth is −0.44 V. Additionally, thermal stabilities are studied with temperature changes from 300 K to 425 K. Moreover, a semi-empirical compact model is presented to visually explain the working principle of the HEB-PFET. [ABSTRACT FROM AUTHOR]

We are pleased to pick up this continuing series on individuals within our community who have made significant impacts in the field of microwaves, and to the world, over the course of their careers. This issue's Microwave Pioneer article is about Mau-Chung Frank Chang, who perhaps more than anyone else, is responsible for the widespread commercial use of the heterojunction bipolar transistor (HBT). Professor Chang is also an example of a researcher who very successfully crossed over from industry to academia and from research to management and back, having spent time in charge of a large team of commercial semiconductor fabrication engineers and as President of a major academic university. Throughout his very varied career, he always emphasized two things: the first he attributes to his mother's teaching - the great power of connecting individuals together to solve problems rather than trying to lead them to a solution, and the second – which is all his own – the fortitude to take on and stick with challenges that seemed daunting to others. We think you will benefit from hearing Frank's story and in getting to know him on a more personal level.

In this study, we conduct a comprehensive examination of the influence of hydrogen (H2) carrier gas flux on the uniformity of epitaxial layers, specifically focusing on the InGaP single layer and the full structure of the InGaP/GaAs heterojunction bipolar transistor (HBT). The results show that an elevated flux of H2 carrier gas markedly facilitates the stabilization of layer uniformity. Optimal uniformity in epitaxial wafers is achievable at a suitable carrier gas flux. Furthermore, this study reveals a significant correlation between the uniformity of the InGaP single layer and the overall uniformity of HBT structures, indicating a consequential interdependence. [ABSTRACT FROM AUTHOR]

RF PAs need to be reliable enough to protect them from damage under load mismatch conditions. This paper investigated the characteristics of GaAs heterojunction bipolar transistors (HBTs) under load mismatch conditions using a novel reverse wave injection technique to realize large VSWR ruggedness measurement with the circle centered at 50 Ohm and optimal impedance separately to analyze the device in real applications. With a real-time waveform measurement system, the RF voltage and current waveform information can be acquired, which provide a more-accurate view of what is occurring at the current generator plane of the HBT device. Thereby, the potential failure mechanisms and load impedance can be identified to design the most-suitable PA circuits in communication systems. [ABSTRACT FROM AUTHOR]

Introduction. The characteristics of solid-state microwave switches are subject to different requirements depending on the application area and technical problems to be solved. No versatile solution exists that could satisfy all requirements at once. The desire to improve the parameters of switches has led to the emergence of devices based on various technologies. In order to elucidate the current trends and future prospects in the field of switch technologies, semiconductor devices that form the basis of switch circuits should be considered.Aim. To review transistor types used in solid-state switches.Materials and methods. The search and selection of literature sources for review was based on the chronological principle. The search depth for considering the parameters of finished components was no more than 10 years, for considering technologies and structural solutions – more than 10 years. This choice was explained by our desire to trace the history of development and approaches to the creation of semiconductor devices that have led to the emergence of the modern component base. The final array of sources comprised scientific publications presenting factual information on the objects under consideration.Results. The types, structures, materials, characteristics and manufacturing technologies of transistors used in switches are considered. The achievable parameters of the switches based on the considered devices are presented. Conclusion. The choice of a particular transistor type for switches depends on the requirements for the parameters and performance characteristics of the final device. At present, transistor solutions for switches are dominated by field-effect transistors (FETs) of various types: GaAs and GaN transistors with a high electron mobility (HEMT) and Si CMOS FETs implemented by standard as well as silicon-on-insulator and silicon-on-sapphire technologies. The conducted literature review has revealed prospects for the development of technologies based on BiCMOS heterojunction bipolar transistors.

A wideband amplifier up to 50 GHz has been implemented in a 0.25 μm, 200 GHz ft SiGe BiCMOS technology. Die size was 0.7×0.73 mm2. The two-stage design achieves more than 11 dB gain over the whole 20 to 50 GHz band. Gain maximum was 14.2 dB at 47.5 GHz. Noise figure was lower than 9 dB up to 34 GHz and a current of 30 mA was drawn from a 4 V supply. To the author’s best knowledge this is the highest gain bandwidth product of a monolithic SiGe HBT amplifier ever reported.

RF PAs need to be reliable enough to protect them from damage under load mismatch conditions. This paper investigated the characteristics of GaAs heterojunction bipolar transistors (HBTs) under load mismatch conditions using a novel reverse wave injection technique to realize large VSWR ruggedness measurement with the circle centered at 50 Ohm and optimal impedance separately to analyze the device in real applications. With a real-time waveform measurement system, the RF voltage and current waveform information can be acquired, which provide a more-accurate view of what is occurring at the current generator plane of the HBT device. Thereby, the potential failure mechanisms and load impedance can be identified to design the most-suitable PA circuits in communication systems.

A broadband power amplifier in a 250-nm InP HBT technology is presented, working at full $H$ -band (220–320 GHz). A cascode transistor is employed as a power cell to achieve high gain and power at $H$ -band. Two-stage cascode power amplifier is designed with input and output impedance of not 50 but 25 $\Omega $ , reducing the impedance transformation ratio and allowing the broadband matching networks. Two power-amplifier channels are power-combined using on-chip baluns which perform the impedance transformation from 25 to $50~\Omega $ . The balun operation is based on the electromagnetic field conversion between coplanar waveguide and microstrip line. It does not rely on long transmission lines with frequency-dependent length, so that it occupies a very compact area and exhibits a broadband performance. It also enables power amplifiers to operate in the balanced mode, allowing the area reduction and stable operation. Substrate modes and in-band resonances in InP substrate, which seriously degrade circuit performance and limits bandwidth, are effectively suppressed by the reduced on-chip ground and balanced operation. The fabricated power amplifier shows a measured small-signal gain of 20.8 dB at 232 GHz with a 3-dB bandwidth larger than 51 GHz (20.8%). Output power also exhibits a broadband performance of 8.0± 1.5 dBm from 220 to 295 GHz with power gain larger than 10.5 dB, corresponding to a large-signal 3-dB bandwidth larger than 75 GHz. This belongs to an excellent bandwidth in both small- and large-signal performance among the reported $H$ -band power amplifiers.

In this paper the state of the art in RF switches for mm-wave frequency range is summarized and evaluated. Several leading technologies is presented from typical semiconductor devices based on transistors and diodes on Si, SiGe or III-V semiconductor substrates to more unconventional solutions such as microelectromechanical or phase-change material switches. The most important parameters and characteristics for those technologies are gathered and compiled for comparison. Besides different technologies, also various switch topologies of mm-wave switches are presented, assessed and compared. Furthermore, new emerging technological solutions approaching mm-wave range involving two-dimensional materials are also presented. Their evaluation is focused on proposed designs and current results for experimentally evaluated prototypes. Although the performance of these devices are currently not competitive with more traditional approaches, some reported results near the mm-wave range makes them a promising solution for future mm-wave switches and an interesting topic for further research and development.

The biodiversity of Ecuadorian stingless bees is almost 200 species. Traditional pot-honey harvest in Ecuador is mostly done from nests of the three genera selected here Geotrigona Moure, 1943, Melipona Illiger, 1806, and Scaptotrigona Moure, 1942. The 20 pot-honey samples collected from cerumen pots and three ethnic honeys “abeja de tierra”, “bermejo”, and “cushillomishki” were analyzed for qualitative and quantitative targeted 1H-NMR honey profiling, and for the Honey Authenticity Test by Interphase Emulsion (HATIE). Extensive data of targeted organic compounds (41 parameters) were identified, quantified, and described. The three honey types were compared by ANOVA. Amino acids, ethanol, hydroxymethylfurfural, aliphatic organic acids, sugars, and markers of botanical origin. The number of phases observed with the HATIE were one in Scaptotrigona and three in Geotrigona and Melipona honeys. Acetic acid (19.60 ± 1.45 g/kg) and lactic acid (24.30 ± 1.65 g/kg) were particularly high in Geotrigona honey (in contrast to 1.3 g/kg acetic acid and 1.6 g/kg lactic acid in Melipona and Scaptotrigona), and with the lowest fructose + glucose (18.39 ± 1.68) g/100g honey compared to Melipona (52.87 ± 1.75) and Scaptotrigona (52.17 ± 0.60). Three local honeys were tested using PCA (Principal Component Analysis), two were assigned with a correct declared bee origin, but “bermejo” was not a Melipona and grouped with the Scaptotrigona cluster. However after HCA (Hierarchical Cluster Analysis) the three honeys were positioned in the Melipona-Scaptotrigona cluster. This research supports targeted 1H-NMR-based profiling of pot-honey metabolomics approach for multi-parameter visualization of organic compounds, as well as descriptive and pertained multivariate statistics (HCA and PCA) to discriminate the stingless bee genus in a set of Geotrigona, Melipona and Scaptotrigona honey types. The NMR characterization of Ecuadorian honey produced by stingless bees emphasizes the need for regulatory norms. A final note on stingless bee markers in pot-honey metabolites which should be screened for those that may extract phylogenetic signals from nutritional traits of honey. Scaptotrigona vitorum honey revealed biosurfactant activity in the HATIE, originating a fingerprint Honey Biosurfactant Test (HBT) for the genus in this set of pot-honeys.

The synthesis of MMT and poly(o-anisidine) (MMT/POA) clay nanocomposites was carried out by using the chemical oxidative polymerization of POA and MMT clay with POA, respectively. By maintaining the constant concentration of POA, different percentage loads of MMT clay were used to determine the effect of MMT clay on the properties of POA. The interaction between POA and MMT clay was investigated by FTIR spectroscopy, and, to reveal the complete compactness and homogeneous distribution of MMT clay in POA, were assessed by using scanning-electron-microscope (SEM) analysis. The UV–visible spectrum was studied for the optical and absorbance properties of MMT/POA ceramic nanocomposites. Furthermore, the horizontal burning test (HBT) demonstrated that clay nanofillers inhibit POA combustion. [ABSTRACT FROM AUTHOR]

An efficient, broadband SiGe HBT cascode nonuniform distributed power amplifier (NDPA) is presented for low-cost, fully integrated Si-based phased arrays. Optimum load impedances at each SiGe HBT cascode in a four-stage NDPA core are obtained by scaling the characteristic impedance ($Z_{0}$) of the collector transmission lines (TLs) and tapering the SiGe HBT emitter area simultaneously. A novel compact, lumped-element two-section $\lambda $ /4 output impedance transformer (OIT) is proposed to lower the NDPA load impedance ($Z_{L}$) from 50 to 25 $\Omega $ over more than one decade bandwidth (BW). Each $\lambda $ /4 impedance transformer is realized by four cascaded CLC $\pi $ -networks integrated into a single three-turn symmetric inductor in order to achieve compact size, high passive efficiency, and high LC cutoff frequency ($f_{c}$). The systematic design approach of a lumped-element $\lambda $ /4 impedance transformer with an arbitrary $Z_{0}$ is described in detail. The prototype NDPA was fabricated in 0.13- $\mu \text{m}$ SiGe HBT BiCMOS technology. The proposed SiGe HBT cascode NDPA supports both high linearity (HL) and high gain (HG) modes, each suited to a specific application. The NDPA attains a peak power gain of 10.3/12.5 dB, a saturated output power ($P_{\mathrm {out}}$) of 21.3/21.5 dBm, and a power added efficiency (PAE) of 12.2%/12.5%–21.6%/22.0% for HL/HG modes, with a 3-dB BW from 1.5 to 24.0 GHz. The NDPA delivers 13.0-dBm average $P_{\mathrm {out}}$ with a PAE of 10.0% at 6-Gbit/s data rate 64 QAM modulation. [ABSTRACT FROM AUTHOR]

The manufacturing technology for heterojunction bipolar transistor (HBT) is different from the one used for bipolar silicon junction transistor (BJT). The base in case of BJT is manufactured by using diffusion and the diffusion laws determine a Gaussian type of profile in the base. HBT devices are manufactured using molecular epitaxy which gives a contact doping profile. In case of HBT, producing an internal field by using uniform doping is no more possible. This is the reason why was used in the gradation of the molar composition. The Analysis using Octave soft was made for the transit time through the base of the drift HBT transistors type GaAs/AlxGa1-xAs. [ABSTRACT FROM AUTHOR]

Although electronic word-of-mouth via social networking sites (or sWOM) greatly induced online shopping, its importance in shopping decisions during the coronavirus disease (COVID-19) pandemic has not been holistically considered. Based on the necessity of sWOM, uses and gratifications theory (UGT), and health belief theory (HBT), this study frames a consumer shopping tendency model toward sWOM in the context of the pandemic. A web-based survey was designed to collect data from 403 respondents who are inclined to patronize e-stores during the pandemic. Next, the measurement model is examined using a two-step method of structural equation modeling. The findings specify that sWOM is an influential communication mode for online shopping in the pandemic. sWOM is of primary importance to information quality. Moreover, utilitarian value, social value, perceived threat, and self-efficacy toward shopping tendency are significantly motivated by sWOM. Lastly, information quality, utilitarian value, social value, and perceived threat are major predictors of shopping tendency during Covid-19. Finally, theoretical and practical implications are discussed.

Polycyclic aromatic hydrocarbons (PAHs) are recognized as a toxic, mutagenic and/or carcinogenic compounds, and their pollution of soil and aquifer is of increasing environmentally risk. Laccases (E.C. 1.10.3.2) are phenoloxidases catalyze the oxidation of PAHs in the presence of a mediator compound and hyacinth plant. In this study laccase from Trametes versicolor was immobilized into chitosan, and the potential to oxidize anthracene in the presence of 1-hydroxybenzotriazole (HBT) was examined. Results indicated that the immobilization enhanced the stability of laccase against temperature, pH, inhibitors and loading time compared with the other cases. The immobilized laccase-mediator system was as efficient as the free enzyme for oxidizing the tested PAHs. After 24h. of incubation, immobilized laccase–HBT showed a system oxidization more than immobilized laccase without (HBT) of PAHs; Chitosan with hyacinth plant and (HBT) resulted better conversion than chitosan with or without HBT. These results indicate a new chance for applying the immobilized laccase in bioremediation.

This article presents a state-of-art review of on-wafer S-parameter characterization of THz silicon transistors for compact modelling purpose. After, a brief review of calibration/de-embedding techniques, the paper focuses on the on-wafer calibration techniques and especially on the design and dimensions of lines built on advanced silicon technologies. Other information such as the pad geometry, the ground plane and the floorplan of the devices under test are also compared. The influence of RF probe geometry on the coupling with the substrate and adjacent structures is also considered to evaluate the accuracy of the measurement, especially using EM simulation methodology. Finally, the importance of measuring above 110 GHz is demonstrated for SiGe HBT parameter extraction. The validation of the compact model is confirmed thanks to an EM-SPICE co-simulation that integrates the whole calibration cum de-embedding procedure.

Current mirrors (CMs) are essential building blocks for biasing electronic circuits. The present work demonstrates that errors in mirroring ratios increase at cryogenic temperatures, for all types of SiGe HBT and CMOS CMs. The sources of errors are attributed to the mismatch in operating conditions and a combination of process variations and layout effects. In particular, the effects of layout on device current are found to increase significantly at low temperatures, which can potentially contribute more to the CM error than process variations. Among all investigated CM configurations, the simple CM based on large geometry SiGe HBTs is the most versatile option with small errors, a large operational range, and a simple layout. [ABSTRACT FROM AUTHOR]

In this paper, an emitter-length scalable noise and small signal model for InP heterojunction bipolar transistor (HBT) are presented. A set of scalable expressions for noise parameters based on hybrid-π topology in the low-frequency ranges are derived. The analytical and experimental results show that under the same bias condition, good emitter-length scaling of the noise and small signal model parameters can be achieved between 1.6μm ×10 μm, 1.6μm × 20 μm and 1.6μm × 30 μm InP HBTs.

Empirical models have been widely and successfully used in device modeling in the past few decades. However, they are becoming increasingly intricate to accurately capture the complex thermal effects in semiconductor devices. Therefore, the aim of this work is to utilize a general dimension-reduction method to quickly and accurately construct large-signal models of semiconductor devices with consideration of thermal effects. In general, the junction voltage dimension is represented by empirical functions, whereas the junction temperature dimension is described by the first-order Taylor series approximation. The final analytical current model is a combination of two independent sets of empirical functions. These functions are constructed from pulsed I-V measurements at different ambient temperatures. The percentages of different components are controlled by the thermal level. Two commercial InGaP/GaAs heterojunction bipolar transistors are investigated to verify the effectiveness of this method. The large-signal models are implemented in Advanced Design System. Excellent agreement is achieved between measurement and simulation of the I-V characteristics, S-parameters, and power sweeps. The dimension reduction method is able to effectively reduce the number of equations and parameters because the temperature dimension is expanded by using a Taylor series. In addition, this method would be applied to the thermal modeling of various devices based on new materials or process technologies. Accordingly, the dimension reduction method is powerful and useful in fast and accurate thermal modeling of microwave semiconductor devices.

In this study, biogas production efficiencies of mixtures obtained by adding corn silage (CS) to citrus industrial wastes at different ratios were determined. Orange (OJPW) and tangerine processing juice wastes (TJPW) (crusts and shells) were selected as materials in the study. 25%, 50%, 75% of CS was added to these selected wastes. Changes in the obtained mixture chemical properties (dry matter, dry organic matter, crude ash, crude protein, crude oil, Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF)), biogas production and methane content in the biogas were investigated. The results of the study showed that the highest crude protein content was found in 100% TJPW (10%), raw fat percentage in 100% TJPW (5.14%), dry matter content in 100% CS (93.56%), ADF in 100% CS (22.74%) and the NDF in a mixture of 25% OJPW + 75% CS (45.08%). The highest methane production was determined for a mixture of 100% TJPW and 50% TJPW + 50% OJPW (0.46 m3 kg-1 ODM). Also the highest biogas production was determined in a mixture of 50% OJPW + 50% TJPW (0.90 m3 kg-1 ODM). The mixing of CS in TJPW and OJPW reduced significantly the production of methane and biogas in the mixture. As a result of the statistical analysis, significant differences (P≤0.05) were found in both methane and biogas production of agricultural wastes.

Copyright of Al-Mustansiriyah Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Hanbury Brown and Twiss (HBT) interferometer was proposed to observe intensity correlations of starlight to measure a star's angular diameter. As the intensity of light that reaches the detector from a star is very weak, one cannot usually get a workable signal-to-noise ratio. We propose an improved HBT interferometric scheme incorporating optical parametric amplifiers (OPA) into the system to amplify the correlation signal. Remarkably, for weak star light, the signal-to-noise ratio (SNR) in the new HBT interferometric scheme is much better than that of conventional HBT interferometer. Our work is valuable in measuring a star whose intensity at the detector is low and maybe also applicable in remote sensing and long-distance quantum imaging where the light passed through the object is weak after a long distance transmission. [ABSTRACT FROM AUTHOR]

A novel ballast resistor network is proposed to achieve a better thermal management in HBT power cells without degrading the RF performances. Experiments were conducted on two HBT power amplifiers. They occupy same area. One is designed using conventional ballast network. The other uses proposed novel network. Temperature comparisons were made based on the same current density. Infrared camera images show that a more uniform temperature distribution is obtained in novel ballast network power amplifier. Our results demonstrate that the proposed novel ballast network has promising applications in high power amplifiers. (C) 2008 Wiley Periodicals, Inc.

Hydrazine (N 2 H 4), a chemical compound widely used in various industrial applications, causes significant environmental and biological hazards. Therefore, it is crucial to develop methodologies for the visualization and real time tracking of N 2 H 4. In this regard, we have constructed a novel near-infrared fluorescent probe (HBT-Cy) that can effectively detect N 2 H 4 in various samples. HBT-Cy contains 2-(2′-hydroxyphenyl)benzothiazole (HBT), cinnamoyl (Cy), and pyridinium (Py) moieties. Importantly, HBT-Cy exhibits a rapid, selective, and highly sensitive response to N 2 H 4. This response results in the release of HBT-Py and the generation of considerable colorimetric changes along with a significant NIR (near infrared) fluorescence signal, peaking at 685 nm. Advantages of this system include turn on NIR fluorescence with large Stokes shift, (approximately 171 nm), low limit of detection (LOD = 0.11 μM) and quantum yield (0.211). The probe with low cytotoxic behavior demonstrates strong NIR fluorescence imaging capabilities to visualize endogenous and exogenous N 2 H 4 in live cells. This mitochondria-targetable probe shows effective subcellular localization. These results suggest that HBT-Cy is a valuable probe for tracking and investigating the behavior of N 2 H 4 in biological systems and environmental samples. [Display omitted] • A novel NIR emissive probe (HBT-Cy) was synthesized for the detection of N 2 H 4 in vapor or solution. • The probe has low cytotoxicity, large Stokes shift with low detection limit (0.11 μM). • The probe was capable of on-site detection of N 2 H 4 in soil, water, and plant samples. • Smartphone and paper kit applications allow to determine N 2 H 4 on site. • The probe could be targeted to mitochondria in living cells to visualize N 2 H 4. [ABSTRACT FROM AUTHOR]

Within many years microelectronics developed based on p-n junctions made of germanium or silicon, namely on homojunctions (BJT). In this case the main technological difficulty was to control the level of doping concentrations. Semiconductor structures were obtained by the variation of type and concentration of the doping impurities. A new phase of the evolution of the semiconductor devices is the manufacturing and large scale using of heterojunctions. Heterojunction is the contact of two semiconductors, different according to the chemical composition, existing in a single crystal. Within this contact not only the energetic areas structure varies, but also the effective body of the carriers, their mobility and other parameters. The possibility of variation of these parameters allows the manufacture of unique devices that have record performance. Heterojunction bipolar transistors (HBT) have the following benefits: static gain in current, high cutting frequency, high speed of conversion, low temperature running. The aim of my study is transit time study through the base in case of drift transistors. [ABSTRACT FROM AUTHOR]

Terahertz band has recently attracted the attention of the communication society due to its huge bandwidth and very high-speed wireless communications capability. It has been utilized in a variety of disciplines including physics, biology and astronomy for years; and the main concerns have always been obtaining highly efficient and high-power terahertz sources. Today, these problems are still the most important issues in establishing an operable wireless terahertz communication link. In this paper, recent studies in the field of terahertz source design are investigated based on the terahertz output power and efficiency. Solid-state sources and optical sources were comparatively reviewed with optical photoconductive material (OPM)-based methods which are combined with the terahertz antennas in the design phase generally. For wireless communication, the most suitable frequencies are between 0.3 THz and 1 THz due to the attenuation profile of the atmosphere. For this reason, based on the recently published studies, it has been observed that OPM and resonant tunneling diode-based sources are the most promising terahertz sources in terms of efficiency and power. Key issues and the main problems of terahertz photoconductive antennas which are the base of OPM method were also discussed in this paper. [ABSTRACT FROM AUTHOR]

Electrical discharge damage is an unpredictable source of yield loss and a constant challenge to device reliability for the micro-electronics industry. There is considerable history and established methodology for handling charging effects for the silicon semiconductor sector, but literature is generally limited for GaAs and III–V compound semiconductor manufacturing. In this paper, electrical charging and subsequent discharge defects created during isolation implant processing of epitaxial wafers combining hetero-junction bipolar transistor and HEMT are discussed. As is common in semiconductor fabrication, a combination of the circuit layout, process sequence and tool configuration formed the ideal condition for a surge of electrical charging related yield failures. Through extensive examination and analysis, the primary source and mechanism of the failure were identified. These findings lead to development of proper detection and the resolution of the issue through key process improvements that ultimately enhanced yield and the GaAs integrated circuit die robustness against charging induced damage. [ABSTRACT FROM AUTHOR]

In this study, biogas production efficiencies of mixtures obtained by adding corn silage (CS) to citrus industrial wastes at different ratios were determined. Orange (OJPW) and tangerine processing juice wastes (TJPW) (crusts and shells) were selected as materials in the study. 25%, 50%, 75% of CS was added to these selected wastes. Changes in the obtained mixture chemical properties (dry matter, dry organic matter, crude ash, crude protein, crude oil, Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF)), biogas production and methane content in the biogas were investigated. The results of the study showed that the highest crude protein content was found in 100% TJPW (10%), raw fat percentage in 100% TJPW (5.14%), dry matter content in 100% CS (93.56%), ADF in 100% CS (22.74%) and the NDF in a mixture of 25% OJPW + 75% CS (45.08%). The highest methane production was determined for a mixture of 100% TJPW and 50% TJPW + 50% OJPW (0.46 m3 kg-1 ODM). Also the highest biogas production was determined in a mixture of 50% OJPW + 50% TJPW (0.90 m3 kg-1 ODM). The mixing of CS in TJPW and OJPW reduced significantly the production of methane and biogas in the mixture. As a result of the statistical analysis, significant differences (P=0.05) were found in both methane and biogas production of agricultural wastes. [ABSTRACT FROM AUTHOR]

This paper provides insight into the transport mechanisms of the collector current in SiGe HBTs operating at cryogenic temperatures and compares three technology generations of devices. Based on the experimental data, a method to differentiate direct tunneling from quasi-ballistic transport is proposed. Measurements indicate that direct tunneling becomes more significant at cryogenic temperatures. The effects of technology scaling on the direct tunneling were investigated using TCAD. Direct tunneling was found to be sensitive to the base width and the Ge profile. It is predicted that without an increase in the Ge content, direct tunneling may dominate over quasi-ballistic transport at the limits of technology scaling. [ABSTRACT FROM AUTHOR]

Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O 2 to H 2 O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila , respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 μM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification. [ABSTRACT FROM AUTHOR]

This work presents multivariate regression polynomial as a versatile and efficient method for DC modeling of modern transistors with very different underlying physics including MOSFET (metal-oxide-semiconductor field-effect transistor), MESFET (metal–semiconductor field-effect transistor), HBT (heterojunction bipolar transistor), HEMT (High-electron-mobility transistor) and a novel silicon-on-insulator four-gate transistors (G4FET). A set of available data from analytic solution, TCAD simulation, and experimental measurements for different operating conditions is used to empirically determine the parameters of this model and a different set of test data is used to verify its predictive accuracy. The developed model expresses the drain current as a single multivariate regression polynomial with its validity spanning across different possible operating regions as long as the chosen independent variables lie within the range of training data set. The continuity of the resulting polynomial and its first and second order derivatives make it particularly suitable for implementation in a circuit simulator. The model also provides a method for further simplification based on prior knowledge of the underlying physical mechanism and shows excellent predictive capability for different kinds of devices. This can be very useful for modeling deep-submicron emerging devices for which any closed-form analytical solution is not yet available. [ABSTRACT FROM AUTHOR]

A compact highly efficient high-power SiGe Ka-band balanced frequency doubler is presented. Using a compact single-footprint four-way transformer input balun, wideband matching, and high fundamental rejection were achieved simultaneously. A cascode topology with very low base impedance termination was utilized for stable operation and high-voltage swing at the output. Two cascode differential pairs form a common-centroid configuration, resulting strong enhancement in output power, power-added efficiency (PAE), fundamental rejection, and robustness to process and supply variation. The proposed Ka-band cascode balanced frequency doubler was implemented in a 0.13- $\mu \text{m}$ SiGe BiCMOS technology. Measured results show 13-dBm output power with 22% peak PAE at 34 GHz for a −1-dBm input power. The 3-dB conversion gain bandwidth is from 25 to 40 GHz, fully covering Ka-band. Peak fundamental suppression is 74.5 dB at 33 GHz, and it is higher than 35 dB over Ka-band. No performance degradation is observed after 24-h RF stress test. To the author’s best knowledge, this paper has the highest efficiency, the highest output power/power density, the highest conversion gain without output buffers, and the higher or comparable fundamental rejection among any Si-based frequency doublers. Therefore, this doubler will be a promising solution for efficient and high-power local oscillator generation in 5G wireless phased-array communication system. [ABSTRACT FROM AUTHOR]

We report an InP/InGaAs/InP double heterojunction bipolar transistor fabricated in a triple-mesa structure, exhibiting simultaneous 404 GHz fτ and 901 GHz fmax. The emitter and base contacts were defined by electron beam lithography with better than 10 nm resolution and smaller than 20 nm alignment error. The base-collector junction has been passivated by depositing a SiNx layer prior to benzocyclobutene planarization, improving the open-base breakdown voltage BVCEO from 3.7 to 4.3 V.

This paper reviews the state of emerging transistor technologies capable of terahertz amplification, as well as the state of transistor modeling as required in terahertz electronic circuit research. Commercial terahertz radar sensors of today are being built using bulky and expensive technologies such as Schottky diode detectors and lasers, as well as using some emerging detection methods. Meanwhile, a considerable amount of research effort has recently been invested in process development and modeling of transistor technologies capable of amplifying in the terahertz band. Indium phosphide (InP) transistors have been able to reach maximum oscillation frequency (fmax) values of over 1 THz for around a decade already, while silicon-germanium bipolar complementary metal-oxide semiconductor (BiCMOS) compatible heterojunction bipolar transistors have only recently crossed the fmax = 0.7 THz mark. While it seems that the InP technology could be the ultimate terahertz technology, according to the fmax and related metrics, the BiCMOS technology has the added advantage of lower cost and supporting a wider set of integrated component types. BiCMOS can thus be seen as an enabling factor for re-engineering of complete terahertz radar systems, for the first time fabricated as miniaturized monolithic integrated circuits. Rapid commercial deployment of monolithic terahertz radar chips, furthermore, depends on the accuracy of transistor modeling at these frequencies. Considerations such as fabrication and modeling of passives and antennas, as well as packaging of complete systems, are closely related to the two main contributions of this paper and are also reviewed here. Finally, this paper probes active terahertz circuits that have already been reported and that have the potential to be deployed in a re-engineered terahertz radar sensor system and attempts to predict future directions in re-engineering of monolithic radar sensors.

Bose–Einstein correlations for same-sign charged pions from proton–proton collisions at s = 7 TeV are studied by the Large Hadron Collider beauty (LHCb) experiment. Correlation radii and chaoticity parameters are determined for different regions of charged-particle multiplicity using a double-ratio technique and a Levy parametrization of the correlation function. The correlation radius increases with the charged-particle multiplicity, while the chaoticity parameter decreases, which is consistent with observations from other experiments. A similar study for proton-lead collisions at s N N = 5.02 TeV is proposed. These results can give valuable input for the theoretical models that describe the evolution of the particle source, probing both its potential dependence on pseudorapidity region and differences between proton–proton and proton–lead systems.

The study presents a comparative analysis between the classic bipolar silicon junction transistor (BJT) and AlGaAs/GaAs heterojunction bipolar transistor (HBT), pointing out the benefits of the latter. The mathematical simulation of the specific physical processes in the two devices is accompanied by a numerical analysis using Matlab application. The computer analysis highlights the benefits of using HBT transistors, namely: static amplification factor with values of 1000-2000 and a transition frequency of 400-500 GHz. [ABSTRACT FROM AUTHOR]

Breaking through diffraction limit at terahertz frequencies is currently performed with the near-field scanning optical microscopy, which suffers from low integration and sensitivity limitations. In this paper, a solid-state superresolution imaging device in 130-nm SiGe BiCMOS technology operating around 534–562 GHz is presented. The device exhibits a single-chip integration of the complete imaging functionality, including a tunable CW illumination source, near-field sensing, and power detection with a high response of up to 9.65 \mu \textA and a noise-equivalent power of around 15–21 pW /\sqrt \text Hz at 60 kHz. Here, the stopband characteristics of a novel cross-bridged double split-ring resonator are exploited as an object-tunable transmission gate between a 3-push Colpitts oscillator and a simple HBT power detector. The resonator features a 3-D topography to achieve high-spatial confinement of the surface near-fields and is capable of resolving structural details with an estimated lateral resolution down to 10–12 \mu \textm . For a separate antenna-coupled oscillator breakout, a radiated power of up to 28.2 \mu \textW was measured. Furthermore, a 2-D raster-scanned superresolution image with a remarkable signal-to-noise ratio of 42 dB was captured for the device operating even at dc. [ABSTRACT FROM PUBLISHER]